diff --git a/internal/rdb/rdb.go b/internal/rdb/rdb.go
index fde76b9..9ee829d 100644
--- a/internal/rdb/rdb.go
+++ b/internal/rdb/rdb.go
@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"strconv"
 	"time"
 
 	"github.com/go-redis/redis/v7"
@@ -165,9 +164,10 @@ func (r *RDB) schedule(zset string, processAt time.Time, msg *TaskMessage) error
 	return nil
 }
 
-// Kill sends the task to "dead" set.
+// Kill sends the task to "dead" queue from in-progress queue, assigning
+// the error message to the task.
 // It also trims the set by timestamp and set size.
-func (r *RDB) Kill(msg *TaskMessage) error {
+func (r *RDB) Kill(msg *TaskMessage, errMsg string) error {
 	const maxDeadTask = 10
 	const deadExpirationInDays = 90
 	bytes, err := json.Marshal(msg)
@@ -175,12 +175,25 @@ func (r *RDB) Kill(msg *TaskMessage) error {
 		return fmt.Errorf("could not marshal %+v to json: %v", msg, err)
 	}
 	now := time.Now()
-	pipe := r.client.Pipeline()
-	pipe.ZAdd(deadQ, &redis.Z{Member: string(bytes), Score: float64(now.Unix())})
 	limit := now.AddDate(0, 0, -deadExpirationInDays).Unix() // 90 days ago
-	pipe.ZRemRangeByScore(deadQ, "-inf", strconv.Itoa(int(limit)))
-	pipe.ZRemRangeByRank(deadQ, 0, -maxDeadTask) // trim the set to 100
-	_, err = pipe.Exec()
+	// KEYS[1] -> asynq:in_progress
+	// KEYS[2] -> asynq:dead
+	// ARGV[1] -> TaskMessage value
+	// ARGV[2] -> error message
+	// ARGV[3] -> died_at UNIX timestamp
+	// ARGV[4] -> cutoff timestamp (e.g., 90 days ago)
+	// ARGV[5] -> max number of tasks in dead queue (e.g., 100)
+	script := redis.NewScript(`
+	redis.call("LREM", KEYS[1], 0, ARGV[1])
+	local msg = cjson.decode(ARGV[1])
+	msg["ErrorMsg"] = ARGV[2]
+	redis.call("ZADD", KEYS[2], ARGV[3], cjson.encode(msg))
+	redis.call("ZREMRANGEBYSCORE", KEYS[2], "-inf", ARGV[4])
+	redis.call("ZREMRANGEBYRANK", KEYS[2], 0, -ARGV[5])
+	return redis.status_reply("OK")
+	`)
+	_, err = script.Run(r.client, []string{inProgressQ, deadQ},
+		string(bytes), errMsg, now.Unix(), limit, maxDeadTask).Result()
 	return err
 }
 
diff --git a/internal/rdb/rdb_test.go b/internal/rdb/rdb_test.go
index 3ee37f3..7717b7a 100644
--- a/internal/rdb/rdb_test.go
+++ b/internal/rdb/rdb_test.go
@@ -115,35 +115,80 @@ func TestDone(t *testing.T) {
 func TestKill(t *testing.T) {
 	r := setup(t)
 	t1 := newTaskMessage("send_email", nil)
+	t2 := newTaskMessage("reindex", nil)
+	t3 := newTaskMessage("generate_csv", nil)
+	errMsg := "SMTP server not responding"
+	t1AfterKill := &TaskMessage{
+		ID:       t1.ID,
+		Type:     t1.Type,
+		Payload:  t1.Payload,
+		Queue:    t1.Queue,
+		Retry:    t1.Retry,
+		Retried:  t1.Retried,
+		ErrorMsg: errMsg,
+	}
+	now := time.Now()
 
 	// TODO(hibiken): add test cases for trimming
 	tests := []struct {
-		dead     []sortedSetEntry // inital state of dead queue
-		target   *TaskMessage     // task to kill
-		wantDead []*TaskMessage   // final state of dead queue
+		inProgress     []*TaskMessage
+		dead           []sortedSetEntry
+		target         *TaskMessage // task to kill
+		wantInProgress []*TaskMessage
+		wantDead       []sortedSetEntry
 	}{
 		{
-			dead:     []sortedSetEntry{},
-			target:   t1,
-			wantDead: []*TaskMessage{t1},
+			inProgress: []*TaskMessage{t1, t2},
+			dead: []sortedSetEntry{
+				{t3, now.Add(-time.Hour).Unix()},
+			},
+			target:         t1,
+			wantInProgress: []*TaskMessage{t2},
+			wantDead: []sortedSetEntry{
+				{t1AfterKill, now.Unix()},
+				{t3, now.Add(-time.Hour).Unix()},
+			},
+		},
+		{
+			inProgress:     []*TaskMessage{t1, t2, t3},
+			dead:           []sortedSetEntry{},
+			target:         t1,
+			wantInProgress: []*TaskMessage{t2, t3},
+			wantDead: []sortedSetEntry{
+				{t1AfterKill, now.Unix()},
+			},
 		},
 	}
 
 	for _, tc := range tests {
 		flushDB(t, r) // clean up db before each test case
+		seedInProgressQueue(t, r, tc.inProgress)
 		seedDeadQueue(t, r, tc.dead)
 
-		err := r.Kill(tc.target)
+		err := r.Kill(tc.target, errMsg)
 		if err != nil {
-			t.Error(err)
+			t.Errorf("(*RDB).Kill(%v, %v) = %v, want nil", tc.target, errMsg, err)
 			continue
 		}
 
-		data := r.client.ZRange(deadQ, 0, -1).Val()
-		gotDead := mustUnmarshalSlice(t, data)
-		if diff := cmp.Diff(tc.wantDead, gotDead, sortMsgOpt); diff != "" {
+		gotInProgressRaw := r.client.LRange(inProgressQ, 0, -1).Val()
+		gotInProgress := mustUnmarshalSlice(t, gotInProgressRaw)
+		if diff := cmp.Diff(tc.wantInProgress, gotInProgress, sortMsgOpt); diff != "" {
+			t.Errorf("mismatch found in %q; (-want, +got)\n%s", inProgressQ, diff)
+		}
+
+		var gotDead []sortedSetEntry
+		data := r.client.ZRangeWithScores(deadQ, 0, -1).Val()
+		for _, z := range data {
+			gotDead = append(gotDead, sortedSetEntry{
+				msg:   mustUnmarshal(t, z.Member.(string)),
+				score: int64(z.Score),
+			})
+		}
+
+		cmpOpt := cmp.AllowUnexported(sortedSetEntry{})
+		if diff := cmp.Diff(tc.wantDead, gotDead, cmpOpt, sortZSetEntryOpt); diff != "" {
 			t.Errorf("mismatch found in %q after calling (*RDB).Kill: (-want, +got):\n%s", deadQ, diff)
-			continue
 		}
 	}
 }